/Engine/Source/Runtime/SlateCore/Public/Layout/ArrangedChildren.h
Add an arranged widget (i.e. widget and its resulting geometry) to the list of Arranged children.
void AddWidget ( [EVisibility](API\Runtime\SlateCore\Layout\EVisibility) VisibilityOverride, const [FArrangedWidget](API\Runtime\SlateCore\Layout\FArrangedWidget) & InWidgetGeometry )